1. Field of the Invention
The present invention relates to a brush seal device. More particularly, the present invention relates to a brush seal device having a brush seal mounted on one of two components displaceable relatively between the two components, wherein the brush seal is capable of resiliently deforming to follow the change of the clearance between the two components even if the relative change between the two components occurs.
2. Description of the Related Art
As one related to the present invention there exists a brush seal device 100, as shown in FIG. 8. FIG. 8 is a sectional view of a brush seal device 100 mounted between a rotary shaft 120 and a casing 110 through which the rotary shaft 120 passes. The casing 110 is a component disposed on the stationary side of a steam turbine or gas turbine. The brush seal device 100 is mounted to the casing 110 to seal fluid by separating the space between the casing 110 and the rotary shaft 120.
The brush seal device 100 is formed in a ring shape and attached to a channel section 112 in the casing 110. Main components of the brush seal device 100 are a brush seal 109, a backing plate 102 and a holding plate 103. In the brush seal 109, a number of bristles 101 are arranged around the circumference to form a partition wall, and on end of the bristles are coupled together to form an attachment section 104. A free end 105 as the other end of the brush seal 109 faces the rotary shaft 120. The diameter of the bristle 101 generally used is 0.02 to 0.5 mm. Tens of thousands or hundreds of thousands of bristles are used.
An annular backing plate 102 is located on one side face of the brush seal 109 with its side face 108 contacting the one side face of the brush seal 109 and supports the bristles 101 against pressure action of the sealed fluid.
A support plate 103 formed as a ring plate is disposed on the other side face of the brush seal 109 to sandwich, in cooperation with the backing plate 102, the brush seal 109 on its attachment section 104 side. The brush seal 109 is exposed at its free end 105 so that the side surface of the brush seal 109 is not wholly sandwiched.
One ends of the backing plate 102, the attachment section 104 of the brush seal 109, and the support plate 103 are welded together to form a connecting section 106.
FIG. 9A is a partial front view of the brush seal 109. The brush seal device 100 in FIG. 9A is in a state that the brush seal 109 and the rotary shaft 120 are normally fitted without oscillation, such that a number of bristles 101 extend straight and oriented to incline relative to the radial direction of the circumefrence of the rotary shaft 120. In the normal state of the brush seal 109, the rotary shaft 120 is in contact with or close to the free end 105, as shown by the solid line in FIG. 8.
FIG. 10A is a perspective view of the free end side of the brush seal 109. In FIG. 10A, the free end 105 is precisely processed by wire electronic discharging or the like such that the brush seal 109 fits the rotary shaft 120 after the process. The bristles 101 are however apt to be deformed, so it is extremely difficult to process them. Moreover, it is also difficult to precisely process the free end 105.
A brush seal device 100B shown in FIG. 11 is another related art to the present invention. FIG. 11 shows thin plates as seals 209 that are piled in the direction of a circumference of a rotary shaft 120 and seal a high pressure area P1 and a low pressure area P2.
Outer circumference portion of the seal 209 is brazed and formed on an attachment section 104 as well as attached to the channel section of the casing 110 through the brazed attachment section 104. Also, a backing plate 102 is located at a side face of the seal 209 in a low pressure area P2, a holding plate 103 is located at a side face in a high pressure area P1, and both the plates 102 and 103 support both sides of the seal 209, respectively.
However, when the rotary shaft 120 eccentrically presses to contact the seal 209 formed in the above way, the piled seals 209 forming an annular body have no space for compensation and thus the spring constant corresponding to the resilient deformation is increased, and thus it is difficult to follow the eccentric behavior of the rotary shaft 120. Thus, clearance between the seals 209 and the outer circumference surface of the rotary shaft 120 is large, and it causes a problem relating to sealing ability for sealed fluid.
Additionally, the pressure of the sealed fluid acts on the seal 209 in the direction of the surfaces of the piled thin plates forming the seal 209 and, as the result, gaps are forcedly increased between the piled plates. Accordingly, also in this case, a problem concerning to the capability to prevent the leakage of fluid to be sealed is present.
Moreover, the brush seal 209 forming an annular body includes some hundreds of thousands thin plates used. Therefore, it is extremely difficult to fabricate the brush seal 209. Further, as the length along the outer circumference of the annular body of the brush seal 209 is longer than that along the inner circumference, spacers are necessarily disposed between thin plates on the outer circumference. However, gaps still remain between the surfaces of the piled plates. In this viewpoint, there also exists the problem of sealing ability. Also, in this constitution such that the flexibility thereof may be reduced, the free end 105 of the brush seal 209 be worn quickly.
In the brush seal device 100A constituted as described above, when the rotary shaft 120 contacts the brush seal 109 involved in any oscillation, oscillation or the like, the brush seal 109 is pressed to contact the rotary shaft 120, and at he same time its tilt angle is increased, as shown in FIG. 9B.
If the pressure of the sealed fluid is the higher P1 in this state, the differential pressure (P1-P2) between the P1 and the low pressure P2 is increased, and the whole straight bristles 101 of the brush seal 109 are pressed against the backing plate and become less deflective, and thus the ability to follow the rotary shaft 120 is worsened.
FIG. 10B is a front view of the brush seal 109 in FIG. 10A, viewed from the free end 105 at inner side.
In FIG. 10A and FIG. 10B, if the sealed fluid flows into gaps between straight bristles 101, each bristle 101 arranged as shown in FIG. 10A, seen from the inner circumference side is pushed aside such that gaps between the bristles 101 are increased as shown in FIG. 10B, and then the sealed fluid leaks from those separated clearances. If this operation is combined with a condition that the bristles 101 in the inclined condition are separated by pressure, one separated side tends to displace such that the inclined angle is decreased, whereby the bristles 101 is deformed such that its length in the radial direction is large, and therefore it increases pressure to the rotary shaft 120 and causes wear.
In addition to a condition like this, with respect to FIG. 8, compared to a position of the brush seal 109 pressed to the rotary shaft 120 (in the condition of FIG. 9B), in the opposite side to the radial direction from axis, a clearance C between a free side surface 105 and the rotary shaft 120 swings as shown in imaginary lines in the rotary shaft 120 of FIG. 8 and opens widely, causing leakage of the sealed fluid from the clearance C.
Also, with respect to a seal 209 in FIG. 11, because thin plates are attached in the direction to which the sealed fluid affects, attached surfaces of the thin plates are separated in the same way as in FIG. 10B if the sealed fluid affects, so that the sealed fluid leaks. In addition, because flexibility of the free end 105 of the seal 209 is inhibited, distance from the rotary shaft 120 should be large, and it causes a problem to the sealing ability and quickens wear.
The present invention has been made in consideration of the problems as mentioned above, and the technical task is to increase the sealing ability even if a clearance is formed between a casing and a rotor by a brush seal.
Also, it is another object to improve the resilient deformation of the brush seal in response to the pressure of the rotary shaft, so that abrasion of the brush seal by the rotary shaft is decreased.
In addition, it is yet another object to obtain good ability of the brush seal to follow in response to the relative displacement between the brush seal and the outer circumference of the rotary shaft to improve the sealing ability.
The present invention has been made to solve the problems as mentioned above, and a technical means for solving the problems is constituted as below. A brush seal of a preferred embodiment according to the present invention is a brush seal device, mounted on one of two components that are relatively rotated, for sealing the clearance given between the two components, comprising:
a brush seal having stacked brush seal units, each brush seal unit comprising: a brush section formed by forming slits in a thin plate at the side opposite to the other component; an attachment section as a base part that is fixed to the one component at the opposite side of the thin plate;
wherein the brush seal is a lamination of the brush seal units as recess layers that has at its free end recesses and the brush seal units as projection layers that has at its free end projections and are stacked in the direction of the pressure of sealed fluid; and
wherein the inner diameter of the projection is different from that of the recess.
In the brush seal device of the preferred embodiment of the present invention, a plurality of brush seal units having a free end facing the surface of the mating component are formed such that each of the thin plates are formed into strips on one side thereof. One is formed with recess layer having larger inner diameter and the other formed with projection layer having smaller inner diameter. Those brush seal units having different diameters are laminated each other to form recess and projection portions on the free end, so that the free end can be flexibly deformed to fit closer to the opposing surface.
In addition, because the recess and projection portion controls the sealed fluid even if a rotor is moved by oscillation such that the free end and the opposing surface of the other component is separated apart, enlargement loss of fluid flowing between the recess and projection portion and loss of thermal dynamic as well as viscous drag are added, so that fluid body resistance is increased such that the amount of leakage of the sealed fluid can be made less.
Moreover, since a brush seal of relative arts is made up of hundreds of thousands of bristles, its inner circumference surface should be precisely processed by wire electric discharging or the like to form accurate circle, the free end of the present invention does not have to be precisely processed because the recess and projection portion increases fluid resistance to cause sealing effect even if a distance between the free end of the brush seal and the other part is increased. This enables an advantage of reduction of manufacturing cost.
In addition, when the rotor as the other component oscillates and presses the brush seal, a clearance C (refer to FIG. 8) is formed at a side symmetrical to the pressed point. However, the recess and projection portion formed in the free end of the brush seal increases fluid resistance, so that sealing effect is increased. Thus, an excellent sealing effect to the oscillating rotor is obtained.
Besides, because the attachment section side of the brush seals is integrated in one body such that base parts of the thin plates without strips formed are stacked, and this structure allows to form the attachment section by simply piling the brush seals, it is much easier to form the attachment section than to form attachment sections by welding hundreds of thousands of bristles.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2001-199038, filed on Jun. 29, 2001, the disclosure of which is expressly incorporated herein by reference in entirety.